A single amino acid change in the yeast vacuolar metal transporters ZRC1 and COT1 alters their substrate specificity.
Iron is an essential nutrient but in excess may damage cells by generating reactive oxygen species due to Fenton reaction or by substituting for other transition metals in essential proteins. The budding yeast Saccharomyces cerevisiae detoxifies cytosolic iron by storage in the vacuole. Deletion of CCC1, which encodes the vacuolar iron importer, results in high iron sensitivity due to increased cytosolic iron. We selected mutants that permitted Deltaccc1 cells to grow under high iron conditions by UV mutagenesis. We identified a mutation (N44I) in the vacuolar zinc transporter ZRC1 that changed the substrate specificity of the transporter from zinc to iron. COT1, a vacuolar zinc and cobalt transporter, is a homologue of ZRC1 and both are members of the cation diffusion facilitator family. Mutation of the homologous amino acid (N45I) in COT1 results in an increased ability to transport iron and decreased ability to transport cobalt. These mutations are within the second hydrophobic domain of the transporters and show the essential nature of this domain in the specificity of metal transport.
Lin
Huilan
H
Department of Pathology, School of Medicine, University of Utah, Salt Lake City, Utah 84132, USA.
Kumánovics
Attila
A
Nelson
Jenifer M
JM
Warner
David E
DE
Ward
Diane McVey
DM
Kaplan
Jerry
J
D000595:Amino Acid Sequence; D001692:Biological Transport; D027682:Cation Transport Proteins / Q000235:genetics / Q000502:physiology*; D015966:Gene Expression Regulation, Fungal; D007501:Iron / Q000737:chemistry; D008670:Metals / Q000737:chemistry; D008969:Molecular Sequence Data; D016296:Mutagenesis; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014617:Vacuoles / Q000378:metabolism; D015032:Zinc / Q000737:chemistry; D001616:beta-Galactosidase / Q000378:metabolism
C076223:COT1 protein, S cerevisiae; D027682:Cation Transport Proteins; D008670:Metals; D029701:Saccharomyces cerevisiae Proteins; C088843:ZRC1 protein, S cerevisiae; D007501:Iron; D001616:beta-Galactosidase; D015032:Zinc